Reciprocating liquid fuel burner



Feb. 6, 1951 w ASSCHER 2,540,416

RECIPROCATING LIQUID FUEL BURNER Filed Jan. 17, 1948 4 Sheets-Sheet l \nveni'o \NiHiam 5.5; A sscher His AH-orneq Feb. 6, 1951 w. B. B. ASSCHER 2,540,416

RECIPROCATING LIQUID FUEL BURNER Filed Jan. 1'7, 1948 4 Sheets-Sheet 2 Fig.2

l I! I0 {I natal/F i i 1 1 II Fig. 8

\nvenrw: \M'Hmm 5.5. Asscher i MZJMZE His AWou-naq Feb. 6, 1951 w. a. B. ASSCHER 2,540,416

RECIPROCATING LIQUID FUEL BURNER Filed Jan. 17, 1948 4 Sheets-Sheet 5 \nveni'or William 5.6. As scher His Ah-crneq Feb. 6, 1951 P w, B B, ASSC ER 2,540,416

RECIPROCATING LIQUID FUEL BURNER Filed Jan. 1'7, 1948 4 Sheets-Sheet 4 Fig? \nvenron William 5.5.Asschar bq M.Zi @4229.

His Afiorneq Patented Feb. 6, 1951 7 2,540,416 RECIPROCATING LIQUID FUEL BURNER William B. B. Asscher, Teddington, England, as-

signor to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application January 17, 1948, Serial No. 2,909 In the Netherlands January 24, 1947 19 Claims. 1

The invention relates to burners for liquid fuel wherein the fuel is atomized and the atomized fuel leaves the atomizing nozzle in the form of a cone. Such atomization may be effected by known means, such as the mechanical energy contained in the fuel itself (i. e., pressure atomization), or the mechanical energy contained in a separate atomizing medium, e. g., steam or air. In other words, the instant invention is applicable generally to liquid fuel burners of the group known as pressure, air'or steam atomizing burners.

When burners of this group are operated under varying loads the pressure of a fluid in the burner also varies; as a result, the spray cone angle varies; such burnersmay, therefore, be designated as being of the type in which the spray angle varies with the load on the burner or,

more specifically, with the pressure of a fluid in the burner. The spray angle is the apex angle of the spray cone.

Combustion air is usually supplied to the burner from the rear of the spray cone, both in the case in which air is used in the atomizing nozzle for atomization or initial combustion, and

in the case in which no other air is introduced into the nozzle. To insure complete combustion, it is necessary that the whole mass of combustion air be contacted intimately with the atomized fuel. When the atomizing burner is mounted within an elongated pre-combustion chamber opening into the mouth of a larger, main combustion chamber, such mixing is best attained when the spray cone is tangent to the mouth of the combustion chamber, i. e., when the spray meets the place where the pre-combustion chamber joins the larger main combustion chamber along an annular line without further impingement against the walls of the pre-combustion chamber, in such a way that all of the main combustion air, moving as an annular forwardly moving stream about the atomizing nozzle and passing through the mouth, cannot enter the larger combustion chamber without crossing the fuel cone.

Consequently, for a given position of the mouth of the combustion chamber with respect to the atomizing head or nozzle, the spray angle must have a specified value. However, as was noted above, most atomizing burners have different spray angles at different loads, and when such burners are to be used under conditions in which the load. is not constant but variable, difhculty has been experienced. Such installations are best designed for the maximum spray angle, because til when the burner is positioned to make the fuel spray tangent to the mouthof the combustion at the smaller spray angle, the spray impinges on the side walls of the pre-combustion space at greater spray angles, resulting in the deposition of coke on the refractory material and frequent shut-downs for cleaning. However, when the burner is correctly located for the maximum spray angle, a decrease in the spray angle upon a change in the load causes the spray cone to enter the main combustion chamber without linking up with the mouth of the chamber, so that air can enter the main combustion space without or with insufficient mixing with the atomized fuel, causing a decrease in the combusziorz efficiency, sometimes to an appreciable ex- It is an object of this invention to provide a liquid fuel atomizing burner of the type in which the spray angle varies with the load on the burner which is automatically adjustable with the load so as to permit the position of the atomizing nozzle to be always in the best location for effecting high combustion efliciency.

It is another object to provide a liquid fuel burner of the type described reciprocally mounted in an elongated pre-combustion chamber and provided withmeans responsive to the load on the burner, e. g., acted upon by the pressure of the fuel or of a separate atomizing medium, for advancing the atomizing nozzle as the spray angle increases and for retracting the atomizing nozzle as the spray angle decreases, so as to maintain the spray cone at all times tangent to the mouth of the main combustion chamber, or substantially so.

A specific object is to provide a mechanism for reciprocating a liquid fuel atomizing nozzle, comprising an element responsive to the pressure of an atomizing fluid supplied to the burner (e. g., the liquid fuel itself, either before introduction into the atomizer, or in the case of a spill type burner, after withdrawal therefrom, or the steam or air) and actuating mechanism connected to the nozzle. Ancillary thereto, it is an object to provide mechanism of the type described wherein the response may be varied or wherein the shape of the parts can be varied to correlate the extent of the reciprocating movement with the pressure to which the pressure responsive element is subjected to conform to the corresponding changes in the spray anglewith .the load.

With these and other objects in view, which will become apparent from the following descripchamber to the fuel tank from which the supply pump takes its suction. By altering, for example, the flow in the return line by means of a control valve, it is possible to vary the pressure in this return line, thereby changing the fuel pressure in the atomizer and regulating the quantity of liquid fuel discharged through the orifice and atomized by the nozzle. However,- this regulation also changes the spray angle. This is illustrated in Fig. 1, wherein I represents the burner tube enclosing fuel supply and return tubes and supporting an atomizing nozzle (not shown in Fig. 1) in its tip. in one .position in solid lines. The burner tube is shown in dotted lines at I in a more forward position. The tube I can be reciprocated longitudinally within a fixed support, represented by bushings 2a and 2b which are part of an air register 2. The register has openings 2h to admit combustion air in regulated amounts about the tube I, the regulation being effected by rotating the outer conical shutter portion having openings 27' which can be brought into registry with the openings 2h. The combustion air flows in two annular currents, separated by partition 2d and may, if desired, be given a rotary motion by inclining the vanes 2e and 21 to provide a helical path. The air enters the pre-combustion chamber defined by the circular-cylindrical wall 3 which may be formed by refractory material, e. g., fireproof masonry. The precombustion chamber widens out at 3a into the main combustion chamber. The cylindrical portion 2g of the air register extends the precombustion chamber rearwardly. For th forward position I of the burner tube, the spray angle corresponding to a low load on the burner is indicated by the angle 4; it will be noted that in this position of the burner tube, and with this spray angle, the spray cone links up with the mouth 3a of the combustion chamber, i. e., it is tangent thereto. The expression "tangent to the mouth of the combustion chamber is intended to indicate a condition wherein the spray cone barely touches the mouth, regardless of whether the mouth is curved, as shown, orangular or of some other shape. As a result all of the combustion air entering through the air register must cross the spray cone of atomized fuel in its passage into the main combustion chamber. Provided that other necessary conditions have been fulfilled (e. g., proper atomization and the proper fuel to air ratio, which conditions are, per se, known in the art) this results in intimate mixing of all of the air with the atomized fuel and in eflicient combustion. However, when the load on the burner is increased, i. e., when the quantity of fuel atomized is increased, by raising the pressure on the fuel return line, the spray angle becomes smaller. This reduced spray angle is indicated by the angle 4. With such a spray angle the spray cone no longer links up with the mouth 3a and the air can enter the main combustion chamber behind the spray cone, i. e., without being mixed thoroughly with the atomized fuel, thereby causing a reduction in the combustion efiiciency which may be indicated, for example, by a decrease in the COz-content of the flue gases.

However, if the burner tube carrying the atomizing nozzle is moved back to the position shown at I the spray cone can again be made to link up with the mouth of the combustion chamber, thereby bringing about favorable com-bustion. According to the instant invention, this shifting of the atomizing nozzle is effected automatically with the load; in the embodiments illustrated in- Figs. 1-3, this is effected by operating the displacement mechanism by the pressure in the fuel return line.

The burner tube is connected. in the rear, by means of flexible tubes to sources of fluids: liquid fuel supply line 5 is connected to a fuel pump to supply fuel at a constant rate, and air, usually under moderate pressure is admitted through a flexible tube I8. The auxiliary air is supplied to the burner tube for discharge close to the liquid spray, e. g., around the atomizing nozzle, for the purpose of effecting initial mixing of the fuel with air and avoiding the deposition of entirely or partly unburned fuel on the burner tip.- The auxiliary air usuall forms a minor part of the total air supplied to the burner. The fuel return line is connected to a flexible tube 6 which discharges into a cylinder 1 which is secured to the rear end of the bushing 2a through a flange ring Ia carried by the cylinder 1. The rear of the cylinder carries a standard 1b which is fixed to a stationary rear guide ring To. From the cylinder the return fuel flows out through a line So and return flow regulating valve 6b to the fuel storage tank. Instead of flexible tubes, I may use rigid pipes with sliding expansion joints, of

the type illustrated in Fig. 7.

The cylinder I is provided with a piston 8 connected to a rack gear 9 and to a tension spring II] which urges the rack gear and piston against the pressure of the return fuel in the cylinder I. The rack gear 9 meshes-with a ring pinion H, rotatable about a bushing which surrounds the rear end of and is adjustably fixed to the burner tube I by means of adjusting bolts I3. These bolts are pivotally secured to the enlarged, rear portion of the tube I and engage bifurcated wings on the bushing I2. The bushing is axially reciprocable within the guide ring 'Ic, flange ring Ia and bushing 2a and is provided with a longitudinal groove I4 and with an inclined cam groove I5, which may be helical or of any shape dependv ing upon the characteristics of the atomizing nozzle. A bolt or cam pin I6 is fixed to the ring 'Ic which 'may be regarded as constituting a rearward portion of the air register 2; the pin I6 extends into the groove I4. A similar cam pin II extends radially inwardly from the pinion II into the groove I5, being carried by and-rotatable with the pinion. The pinion is secured against axial movement by engagement on both front and rear ends thereof with portions of the flange ring Ia and guide ring 10.

The operation of the burner is as follows: In Fig. 2, the piston 8 is shown in its outermost position, i. e., the fuel return pressure is at its highest, and the burner is operating at its maximum load. Corresponding thereto, the burner tube I is shown in Figs. 1 and 3 in its fully retracted position, with the pin I! in the forward portion of the groove I5. If the fuel return pressure is reduced, springs l0 move the piston 8 against the fuel pressure until a new position of equilibrium is reached; the pinion II and cam pin I! are thereby rotated, urging the bushing I2, which is secured against rotation b the cam pin- I6, forwardly as the cam pin I'I runs along the groove I5. By choosing a suitable shape for the groove I5 the displacement of the burner tube can be made to adapt itself to a. change in the fuel return pressure in such a way that the spray cone 9 v burner tube Ijlitil the motion of the pin 65 restores the piston to the position shown in the drawing. I

The response of the burner to changes in pressure may be designed to flt any requirement peculiar to the atomizing nozzle employed by an appropriate choice of the shape of the cam slot 64 It will be understood that while the three specific embodiments involving a bushing with a cam groove, a bell crank linkage, and a servo-motor with a cam lever, respectively, have been described applied to three specific types f burners, these types may be interchangedfihus, for example, it is possible to use the servo motor arrangement of Fig. 7, or any other ervo-motor,

or operating a burner of the types s own in Figs.

1-6. Moreover, it is not necessary that the pressure responsive element, (such as the pistons 8 or 22 or the bellows 59) be acted upon directly by a fluid fed to the burner; they may be acted upon by a separate operating fluid the pressure of which is varied in proportion to the load, e. g.,

by the pressure fluid in a regulator for the burner."

Asa specific example, if the spray angle depends upon the'rate of flow of atomizing air, which. is supplied at approximately constant pressure, by means of a Venturi tube a pressure difierencecan be created which depends on the quantity of air supplied, and this pressure difference can be utilized, if necessary via a servo-motor, for the readjustment of the position of the burner tube.

If desired, the readjustment of the burner tube may be coupled to 'the operating lever for the air register shutter 20, or other means controlling the supply of combustion air, so that both are reset with the aid of one fluid pressure responsive motor. This is illustrated in Fig. 7, where the shutter is provided with a cam 'pin 66 extending through a circumferential slot in the register 2 and into a cam slot 61 in the bushing 43. Reciprocation of the burner tube and bushing 43 will cause the shutter 20 to be rotated to move the holes 27' into or out of registry with the holes 2h.

I claim as my invention:

1. An atomizing burner for liquid fuel comprising a fixed support, a liquid fuel atomizing nozzle of the type in which the spray angle varies with the pressure of a fluid i i'the burner reciprocably mounted with respect to said support, and means responsive to the said pressure of the fluid in the burner for retracting the atomizing nozzle with respect to said support as a change in said pressure causes the spray angle to diminish and for advancing the atomizing nozzle as an opposite change in said pressure causes the spray angle to increase.

2. An atomizing burner for liquid fuel comprising a fixed support, a liquid fuel atomizing nozzle of the type in which the spray angle varies with the pressure of an atomizing fluid in the burner reciprocally mounted with respect to said support, and means responsive to the pressure of said atomizing fluid in the burner for retracting the atomizing nozzle with respect to said support as achange in said pressure causes the spray angle to diminish and for advancing the atomizing nozzle as an opposite change in said pressure causes the spray angle to increase.

3. The burner according to claim 2 wherein the means for retracting and advancing the atomizing nozzle comp-rises a fluid pressure responsive element operatively connected to a liquid fuel line of said burner.

4. The burner according to claim 3, wherein the atomizing nozzle is of the whirler type and is connected to a liquid fuel supply line and to a liquid fuel return line, the atomizing burner is of the type wherein the load is controlled by regulating the pressure inthe fuel return line, and the fluid pressure responsive element is connected to the liquid fuel return line.

5. The burner according to claim 2 wherein the atomizing nozzle is of the whirler type and is connected to a liquid fuel supplyline of said burner, the atomizing burner is of the type in which the load is controlled by regulating the pressure in the fuel supply line, and the fluid pressure responsive retracting means comprises a fluid pressure responsive element operatively connected to the liquid fuel supply line. 1

6. The burner according to claim 2 wherein the atomizing nozzle of the typein which liquid fuel is atomized by means of a gaseous atomizing medium, and the pressure of said gaseous medium is varied with the load on the burner, said atomizer being provided witha supply line for said gaseous atomizing medium, and the said means for retracting and advancing the atomizing nozzle comprises a fluid pressure responsive element connected to said supply line for the gaseous atomizing medium.

-7. An atomizing burner structure for liquid fuel comprising an elongated pre-combustion chamber having a mouth at its forward end connecting with an enlarged combustion chamber, a liquid atomizing nozzle of the type which forms a spray cone of atomized fuel and spray angle of which diminishes with an increase in the pressure of a fluid in the burner and increase with a decrease in said pressure, said nozzle being mounted for reciprocating motion substantially along the longitudinal axis of said pre-jc'ombustion chamber to discharge a spray cone tangentially with respect to said mouth, means for admitting combustion air into the pre-combustion chamber in the rear of the tip of the nozzle for passage through said spray cone, and means responsive to the said pressure of the fluid in the burner for retracting the atomizing nozzle with respect to said pre-combustion chamber as an increase in said pressure causes the spray angle to diminish and for advancing the atomizing nozzle as a decrease in said pressure causes the spray angle to increase. 1

8. The atomizing burner accordingto claim 7 wherein the means for retracting and advancing the atomizing nozzle comprises a fluid pressure responsive element operatively connected for operation in response to the pressure of an atomizing fluid in the burner.

9. An atomizing burner for liquid fuel comprising a fixed support, a liquid fuel atomizing nozzle of the type in which the spray angle varies with the pressure of a fluid in the burner reciprocally mounted with respect to said support, a bushing having a cam surface, a rotatable ring, means inter-connecting said rotatable ring, bushi atomizing nozzle, and fixed support for reciprocating said atomizing nozzle with respect to said support in response to. rotation of said rotatable ring, and a fluid pressure actuated mechanism operatively connected to move in response to the pressure of said fluid in the burner and.

connected to said rotatable ring for rotating .aid ring in a direction to retract the atomizing nizzle as a change in saidpressure causes the spray angle to diminish and fo advancing the atomiz- 

